Advanced in vitro microfluidic tissue models, deemed “tissue chips” or “organs-on-chips”, seek to replicate the complexity of living organisms in a low-cost format suitable for high-throughput experimentation. To date, most such systems have relied on destructive techniques such as immunofluorescence microscopy, or downstream analysis of fluid in the microfluidic path, to report on the activity of the tissue chip under study. In order to provide real-time monitoring capability for tissue chips, we initiated a program to integrate photonic sensors (ring resonators fabricated in silicon nitride) in close proximity to the tissue under study. To date we have succeeded in developing a microfluidic device containing both a nanoporous membrane chip for suspended cell culture, along with a multiplex, antibody-functionalized ring resonator-based photonic sensor chip.

Miniaturized mid-Infrared (mid-IR) spectrometers using integrated photonics and machine learning (ML) were developed to detect the volatile organic compounds (VOCs). The chip-scale spectrometer consisted of an array of microring resonators, where the distributed resonance lines were precise aligned with the VOC characteristic absorption bands. ML technique was implemented in the mid-IR wavelength selection model to improve the spectral efficiency and prevent the spectral crosstalk. To further improve the sensitivity and specificity, the devices surface was functionalized by nano-texturized materials with enhanced molecular affinity and porosity. Our AI enabled mid-IR sensor is essential for remote breath monitoring and point-of-care (POC) diagnostics.

We will present near infrared fluorescent single wall carbon nanotube optical reporters that can measure the spatial and temporal dynamics of neuromodulatory molecules with resolutions that elude conventional methods of inquiry. We will present results on the performance of such sensors on catecholinergic neuromodulators such as dopamine. We will additionally present new approaches for deploying such sensors in biological preparations of varying complexity that permit implementation of the sensors in ways that enable highly resolved imaging of synaptic neurochemical efflux. When combined with post hoc immunofluorescence and super resolution imaging, our approach affords studies of the biophysical properties of single synapses.

In fluorescence-based biosensing applications, to increase optical detection sensitivity, time-resolved measurements are extensively used. Magnetic modulation biosensing (MMB) is a novel, fast, and sensitive detection technology for various applications. While this technology provides high sensitivity detection of biomarkers, to date, only the time resolved signal was analyzed. Here, we use for the first time both time-resolved and spatial-resolved measurements and show that this combination drastically improves the sensitivity of an MMB-based assay.

In early disease stages, biomolecules of interest exist in very low concentrations, presenting a significant challenge for analytical devices and methods. Here, we provide a comprehensive overview of an innovative optical biosensing technology, termed magnetic modulation biosensing (MMB), its biomedical applications, and its ongoing development. In MMB, magnetic beads are attached to fluorescently labeled target molecules. A controlled magnetic force aggregates the magnetic beads and transports them in and out of an excitation laser beam, generating a periodic fluorescent signal that is detected and demodulated. MMB applications include rapid and highly sensitive detection of specific nucleic acid sequences, antibodies, proteins, and protein interactions. Compared with other established analytical methodologies, MMB provides improved sensitivity, shorter processing time, and simpler protocols.

Rapid, highly sensitive, and high-throughput detection of biomarkers at low concentrations is invaluable for early diagnosis of various diseases. In many sensitive immunoassays the protocol is time consuming and requires a complicated and expensive detection system. Here, we demonstrate a high-throughput optical modulation biosensing (ht-OMB) system, which enables reading a 96-well plate within 10 minutes. Using the system, to detect human Interleukin-8, we demonstrated a limit of detection of 0.14 ng/L and a 4-log dynamic range. Testing 94 RNA extracts from 36 confirmed RT-qPCR SARS-CoV-2-positive patients (C_t≤40) and 58 confirmed RT-qPCR SARS-CoV-2-negative individuals resulted in 100% sensitivity and 100% specificity.

In this study, we demonstrate the potential manufacturing method and application of 2D WSe2-based field-effect transistors (2D-FETs) as a promising biosensor for the selective and rapid detection of a pathogen such as SARS-CoV-2 in vitro. The sensors are manufactured by first synthesizing 2D material on Si/SiO2 substrates, followed by photolithography processes to form the FET devices. Then, the surface of 2D material WSe2 has been functionalized with a specific antibody to selectively detect the SARS-CoV-2 spike protein. The TMDC-based 2D-FETs can potentially serve as sensitive and selective biosensors for the rapid detection of infectious diseases.

Infectious diseases are a major problem for both human as well as plant health. Fast and specific detection is needed to combat these diseases. We developed near infrared (NIR) fluorescent nanosensors and used them for fingerprinting of clinically important bacteria and pathogen responses in plants. They are based on single-walled carbon nanotubes (SWCNTs) that fluoresce in the NIR optical tissue transparency window. They were chemically tailored to detect metabolites as well as specific virulence factors (lipopolysaccharides, siderophores,…) and integrated into hydrogel arrays. It allowed us to detect important bacteria (Staphylococcus aureus,…) by remote (≥25 cm) NIR imaging. In another approach we developed nanosensors that change their spectral signature in response to polyphenols, which are released by plants exposed to insects and pathogens. They visualized the plant’s chemical defense remotely in the NIR, which shows the huge potential for monitoring of pathogens.

The world is adopting new vaccination strategies to SARS-CoV-2. The ability of a vaccine to provide immunity can be impacted negatively by mutations in the circulating virus or by non-neutralizing cross-reactive from previous coronavirus infections. It is important to monitor immune response and identify cross-reactivity for antigen mutations and common cold coronavirus strains. To study antibody-antigen interactions in a high throughput and label-free manner we use Arrayed Imaging Reflectometry (AIR). AIR provides information about protein binding for an array with a single CCD image by measuring the change in reflectivity of a silicon/silicon dioxide/protein surface (AIR chip). In this talk we discuss our study in which we use a 37-plex AIR array including Influenza and Coronavirus antigens to study changes in the human immune response to vaccination against SARS-CoV-2. Structural changes to viral surface antigens in Coronaviruses and Influenza viruses can change the immune response to those viruses. This talk will discuss the effect of amino acid mutations in SARS-CoV-2 (SARS2) and related coronaviruses, and structural differences in Influenza virus antigens in terms of their presentation: either recombinantly expressed protein or whole virus particles. We hypothesized that the previously mentioned structural differences would lead to changes in amount of antibody binding and cross-reactivity. We have found that in response to SARS2 vaccination, human subjects have significant increases in antibodies against common cold coronavirus 229E, and that those antibodies strongly correlate with increases in antibodies against SARS2 surface antigen proteins. We also found that increase in 229E antibody binding was more strongly correlated with the S2 subunit of the spike protein of SARS2 than with the S1 subunit. We have also found that there is significantly more antibody binding to the S1 D614G mutant protein than to the wild-type protein, though the antibody binding against the two proteins is strongly correlated. In the future, this technology can help understand antibody response as well as antigen cross-reactivity in response to vaccination and infection.

A surface-enhanced Raman spectroscopy (SERS) substrate for saliva analysis was explored to create a non-invasive tool for pediatric eosinophilic esophagitis monitoring during treatment. Herein, the SERS substrate was developed via the in situ growth of nanoparticles within a paper-fluidic platform. The SERS signal enhancement from different metallic surfaces grown within a filter paper was explored to optimize the signal response.

We report the incorporation of porous silicon on paper towards the realization of a low-cost rapid diagnostic testing platform with the capability for quantification of detected molecules. Real-time optical reflectance measurements of bovine serum albumin adsorption were carried out to benchmark the sensor. Simulations and experiments demonstrate a response-time dependence on porous silicon pore size. Approaches to overcome challenges with porous silicon adhesion on paper and porous silicon membrane mechanical robustness will be discussed.